The present invention relates to the finishing, balancing, and especially refinishing of worn surfaces on rotor members such as disk brake rotors, brake drums, and the like.
In refinishing of variously configured brake rotors and the like, and with reference to FIG. 1, it is customary to provide a rotatable spindle 10, a flange 12 on the spindle, and a cone-shaped member 14 axially slidable relative to the spindle for clamping the rotor or workpiece 15 against the flange, the cone-shaped member engaging a bore diameter 16 of the workpiece opposite the flange. Thus the concentricity of the workpiece relative to the spindle is defined by the engagement with the cone-shaped member, and the perpendicularity of the workpiece relative to the spindle is defined by the engagement with the flange member. A disadvantage of this arrangement is that the sliding fit of the cone member on the spindle permits undesired run out of the cone member relative to the spindle. This problem is exacerbated by the typical need for interchangeability of the cone member with other devices on the spindle. Also, the surface of the workpiece that is engaging the cone member is not necessarily accurately formed, being typically a small chamfer or corner radius 18 between the bore diameter and a face surface of the workpiece opposite the flange member. Even worse, there can be burrs on the workpiece that extend axially toward the cone member from around the bore diameter.
A similar prior art arrangement is disclosed in U.S. Pat. No. 4,708,041 to Granger, wherein the flange 12 is integrally formed as shown in FIG. 2 with a cylindrical core 20 that fits over the spindle 10, the cone member 14 having an enlarged internal diameter for slidably engaging the core. This arrangement permits the clearance between the cone member and the core to be more carefully controlled. However, the concentricity of the core itself introduces a new source of uncertainty in locating the cone member. Also the core has a relatively complex shape that must be accurately formed, and is consequently expensive to produce.
With further reference to FIG. 3, a relatively recent development has the workpiece 15, known as a "composite" rotor, being formed with a stamped steel center hat section 22 that is joined to a cast iron disk member 24. The hat section 22, being relatively thin, is subject to flexing under load, such that conventional refinishing procedures can produce unacceptable tool chattering and run out. In an attempt to avoid these problems, a spring-centering adaptor assembly 26 has been developed wherein the cone member 14 is reversed on the core 20, the flange 12 having a cup-shaped configuration enclosing the cone member 14, a helical spring 28 biasing the cone member 14 away from the flange 12. The workpiece 15 is clamped against the flange member 12 by a clamp member 30 that makes ring contact with the workpiece 15 directly opposite the flange member 12. Although this arrangement overcomes at least some of the undesirable distortion of the hat section 22, other problems remain. For example, the cone member 14 can get stuck on the core 20 such that the spring 28 is ineffective for producing full engagement between the cone member 14 and the workpiece 15. Also, the cone member 14 is subject to excessive runout on the core 20 when there is sufficient clearance for effective operation of the spring 28. Further, the weight of the workpiece 15 can interfere with proper engagement by the cone member 14. Moreover, a high level of skill is required for reasonably accurate centering of the workpiece 15 during clamping.
Thus there is a need for apparatus that can reliably and accurately locate variously configured workpieces, especially composite disk brake rotors, on a rotatable spindle, that is easy to use and inexpensive to produce.